Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/17/21
Area Forecast Discussion
National Weather Service La Crosse WI
1000 PM CST Tue Feb 16 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 222 PM CST Tue Feb 16 2021
We`ll start this discussion off with some good news, as early
afternoon ASOS/AWOS observations showed temperatures above zero
across the entire forecast area, with some spots even getting into
the teens! Now the bad news is that we`ll be getting well below zero
again tonight and some spots could west of the Mississippi River
could get close to wind chills of -20. That said, not thinking we`ll
need an advisory as those wind chills look like they`ll be pretty
spotty with temperatures staying up a bit with as winds become
southerly and clouds move in.
Attention then turns to light snow chances Wednesday as southerly
flow ushers in moisture and some weak isentropic lift spreads in by
the afternoon. Latest short term guidance has trended toward
favoring light snow development across south-central and
southeastern Minnesota into north-central Wisconsin. In addition,
some precip could extend northward from a slightly stronger system
well to the south and possibly clip parts of northeast Iowa and far
southwest Wisconsin. Overall, the forcing looks weak and given the
light southerly flow, moisture return ahead of the forcing will be
lacking quite a bit. As such, many model soundings show that it`ll
be a struggle for enough saturation through the column for precip,
at least for any extended period of time. Still think at least some
light accumulations will be possible for much of the area,
especially given a deep, surface-based DGZ leading to high snow
ratios. If forcing or moisture trend upward, could be a sneaky 1+"
for someone, but as it stands, thinking 3/4 of an inch will be
toward the high end of amounts, but still enough that there could be
a few slick spots.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 222 PM CST Tue Feb 16 2021
Light snowfall overnight Wednesday will end Tuesday morning from
west to east as the short wave exits the region. Some flurries
may persist into Thursday morning as another weak shortwave swings
through the area while some relatively decent saturation remains
in the area.
Otherwise, dry weather is expected to persist into the weekend.
Temperatures begin their slow recovery to near seasonable normals
throughout the week as an upper-level trough progresses eastward
through the central plains and upper midwest of the US. Afternoon
high temperatures will be in the teens to low 20s to the end of the
week. Flow aloft becomes more northwesterly as an upper-level ridge
builds in from the west. As this subtle ridge moves eastward through
the area over the weekend, 850 mb temperatures increase to near -5C
by Sunday with surface temperatures then increasing into the upper
20s to low 30s Sunday afternoon. This warming trend is anticipated
to continue into early next week with ABOVE freezing temperatures
becoming more likely on Monday and Tuesday afternoons.
Another round for precipitation enters the forecast on Sunday.
However, it is still too early to determine exact details, so have
decided to stick with the blended model guidance bringing in some
low chances. This system will be closely monitored as there is a
potential for areas to receive accumulating snow.
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1000 PM CST Tue Feb 16 2021
Cigs: weak upper level shortwave will bringing increasing clouds
overnight, with lowering as Tue wears on. The GFS continues to favor
MVFR cigs for KRST while the NAM and to some extent the RAP does
not. Not finding much in satellite/sfc obs to trend the forecast
toward one solution or the other. Will stick with previous forecasts
and bring MVFR into KRST and hold KLSE VFR. Anticipate refinements
and details become more clear.
WX/vsby: weak shortwave and weak thermodynamics, but with cold air
in place, the forcing could/will be enough to squeeze out light
snow/flurries. Not expecting IFR vsbys, but some dip into MVFR seems
possible/likely. Any accumulation should hold to just a few tenths.
Lesser threat at KLSE.
Winds: staying light through the period, but turning more
Area Forecast Discussion
National Weather Service Dodge City KS
510 PM CST Tue Feb 16 2021
...Updated Aviation Discussion...
.SHORT TERM...(This evening through Wednesday)
Issued at 341 PM CST Tue Feb 16 2021
The arctic airmass was slowly but surely starting to modify --
emphasis on slowly. Here at DDC, we reached +10F early in the
afternoon before stabilizing. We got perhaps a couple of degrees
warmer than forecast, despite the cloud cover and flurries, most
likely due to some mechanical mixing from stronger south winds
today, allowing for mixing of some slightly warmer air just off the
surface. All in all, the forecast update is for tonight through
tomorrow night is not all that different. Tonight`s snow event will
remain just south of southwest Kansas across Oklahoma, and we have
even pulled back some on the Barber County snowfall forecast -- to
around one-half inch (and that would mainly be along the Oklahoma
As far as wind chills go, we expect as temperatures fall back down
toward 0F tonight, wind chills will fall back down to -15 to -18F or
so with continued south wind 7 to 10 mph. A Wind Chill Advisory will
remain in effect (except for the far southwest counties) until mid
to late morning Wednesday.
Today will mark the 9th straight day with temperature below 20F
officially at Dodge City. This ties for 2nd place for longest run
of days below this temperature. That 2nd place was the great
arctic outbreak of 1899, so this is indeed quite the accomplishment
in terms of duration for such an arctic outbreak considering the
period of record for Dodge City goes back to 1875. Number 1 on that
list is the cold wave of late February/early March of 1960 at 11
There is a very reasonable possibility we may push this streak to 10
days tomorrow. The airmass will continue to modify tomorrow, but
will it modify by 10 degrees over today`s high? That will be the
main question. Dodge City will likely start right around 0F early in
the morning, and while there will likely be breaks in the clouds in
the afternoon, the wind will be very light if not calm much of the
afternoon. This will limit mixing and prevent a rapid temperature
rise. In fact, the latest HRRR model runs now keep afternoon
temperatures solidly in the mid teens across southwest Kansas,
including Dodge City, during the time of typical diurnal max of late
.LONG TERM...(Wednesday night through Tuesday)
Issued at 341 PM CST Tue Feb 16 2021
As mentioned in previous Long Term discussions, a much-welcomed
rebound to temperature normalcy is forecast. The transition days
will be Thursday and Friday, but even Thursday may be tough to break
mid 20s across much of the area. Friday, the airmass modification
will continue and much of the snow melt will really commence across
western Kansas. Insolation will go largely into snow melt, so it
will be difficult, even on Friday, to exceed the mid 30s, but it
will certainly feel so much better than the 10F we are seeing this
Another fast-moving, low-amplitude shortwave trough will move out of
the West and across the Rockies over the weekend, but this system
will be moving too quickly to tap into any moisture for
precipitation across southwestern Kansas. We will probably see a
pause in the continued warm-up late in the weekend with slight cold
air advection in the wake of this trough, but the airmass will be
modified substantially by downslope trajectories from Wyoming higher
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 502 PM CST Tue Feb 16 2021
BUFR soundings continue to indicate a layer of moisture in the
1000 to 5000ft AGL level overnight and early Wednesday across
southwest Kansas. Models however differ on where the low ceilings
will be located in this moist layer. Based on the latest trends of
the short term models it appears that ceilings will begin in the
1000 to 2000ft AGL level tonight and then begin to improve after 12z
Wednesday into the 2000 to 3000ft AGL level. After 18z there may
even be a few breaks of sun as ceilings increase to greater than
3000ft AGL. Southeast winds at around 10 knots early tonight will
become light and variable early Wednesday morning.
.PRELIMINARY POINT TEMPS/POPS...
DDC -1 17 3 27 / 10 0 0 0
GCK -2 18 3 25 / 0 0 0 0
EHA 2 21 8 28 / 0 0 0 0
LBL -3 17 2 26 / 10 0 0 0
HYS -1 19 3 27 / 0 0 0 0
P28 4 17 5 26 / 40 10 0 0
Wind Chill Advisory until 10 AM CST /9 AM MST/ Wednesday for
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
659 PM CST Tue Feb 16 2021
Overall, forecast is in good shape at the present time. Made some
minor adjustments to the grids, the main being to add a mention of
snow possibly mixing in across our extreme northern CWA with the
onset of the precipitation. HRRR model soundings look favorable for
this before the warm nose strengthens by midnight.
.PREV DISCUSSION... /ISSUED 523 PM CST Tue Feb 16 2021/
VFR conditions prevail, but MVFR then IFR conditions are expected
overnight as moisture increases across the area. As the moisture
increases, areas of freezing rain will be expected across the
northern areas with AUS the most impacted. Will prevail freezing
rain and sleet there as some sleet will also be possible. For SAT
will tempo the mention of freezing rain as probabilities are less to
the south. Precipitation should move east of the terminals by 12z
with LIFR conditions possibly persisting through the morning and into
the afternoon hours tomorrow.
PREV DISCUSSION... /ISSUED 339 PM CST Tue Feb 16 2021/
.DANGEROUS WINTER WEATHER CONDITIONS TO CONTINUE THROUGH
* Another round of mainly freezing rain and sleet will returns to
South Central Texas tonight with a second round of Wintry Mix
expected tomorrow night into Thursday. Additional ice
accumulations will combine with existing ice on the ground to make
outdoor travel dangerous through Thursday. If you must travel, keep
an extra flashlight, food, blankets, and water in your vehicle in
case of an emergency.
* Rotating power outages expected to continue.
* Check frequently on those without heat and water. Protect plants
and pipes. Provide warm shelter for pets.
SHORT TERM (Today through Wednesday)...
While we had another day of sunshine for most of the morning
temperatures have remained below freezing across South Central Texas.
Low 20s to a few `lucky` areas seeing lower 30s are where
temperatures are this afternoon. As of now cloud cover has begun to
spread into South Central Texas from the south and from the
northwest. While some western areas may see the sun again tomorrow,
areas along the I-35 corridor will be entering another cloudy and
wintry weather pattern.
Synoptically the CONUS is experiencing a large scale trough with
embedded shortwaves. One of those shortwaves will move across north
Texas overnight tonight into tomorrow. At the same time a surface low
pressure system will form across the middle Texas Coast. It is these
two features that will provide the lift needed for the next round of
wintry precipitation on the way tonight.
Model soundings support mainly a freezing rain pattern for tonight as
overnight lows again drop into the 20s area wide due to cold air
advection at the surface. In the mid-levels areas of warm air
advection will work to produce a slight warm nose. This could lead to
some sleet mixing in across parts of the Hill Country, Austin Metro
and parts of Williamson and Lee Counties. This will end up being a
bit of a saving grace across these areas in terms of overall ice
accumulations. In general across theses areas as much as a tenth
(0.10) of an inch of new ice accumulation is possible. A few areas
may see as much as a quarter (0.25) inch of new ice, especially
across parts of Williamson and Lee Counties, but again, if more sleet
is able to mix in these overall accumulations will be lower. Further
south along the I-35 corridor towards the San Antonio, along the
Coastal Plains and west across the Edwards Plateau as much as 0.05
inches of new ice are possible. In terms of timing the two areas of
precipitation should begin to form late this evening into the
overnight hours: one across the Hill Country with the shortwave, and
the other across the southern Edwards Plateau and Coastal Plains with
the Coastal Low. Precipitation should fill in and become widespread
across all of South Central Texas by midnight. While no one should be
out on the roads or really considering travel at this point,
precipitation does generally come to an end after sunrise tomorrow,
with lingering mix of rain and freezing rain east of Interstate 35
through the late morning to the noon hour. Tomorrow afternoon looks
dry across the area with some sunshine returning across the Rio
Grande and Edwards Plateau. Afternoon highs should range from the low
30s across northern areas to the upper 40s and 50s in area that see
sunshine. This should at least start to help melt the snow and ice
across some areas.
Takes Deep Breath, looks for the light at the end of the tunnel, one
more event to go! The base of the trough will finally move across
Texas Wednesday night into Thursday morning. Models are still iffy
with this event, having pushed it back more into the day on Thursday
which will be discussed below. Of the two events (tonight vs.
tomorrow night) this is certainly the lower confidence of the two,
but it has started to become a clearer picture today. Rain mixed with
freezing rain should begin during the evening and early overnight
hours Wednesday across the Rio Grande Plains and then spread eastward
through the night, changing to a wintry mix of freezing rain, sleet,
and snow after midnight. Accumulations with this activity are
expected to generally be light, but certainly won`t help the ongoing
situation with snow (from Sunday night) and ice (from tonight) on the
Based on the uncertainty with the second system we have elected to
make no changes at this time to our Winter Weather Hazards. A Winter
Storm Warning is in effect for most of the area due to the threat of
ice accumulations with tonights system. With lower impacts along the
Rio Grande for tonights event have continued the Winter Weather
Advisory in those areas. Future shifts will need to look at the
second event and determine if an upgrade to Winter Storm Warning is
needed, or if the Winter Weather Advisory will suffice.
LONG TERM (Wednesday Night through Monday)...
Wintry precipitation chances hold over into the day on Thursday as
the base of an upper level trough advances across the region with a
tailing cold front. The latest thinking is for the greatest
concentration of wintry precip will occur to the west of I-35 across
the Rio Grande Plains and Southern Edwards Plateau. For further
east, couldn`t rule out a slight chance for wintry mix. Considerable
uncertainty remains regarding this expected final round of wintry
precip as the latest model guidance vary on the amount of QPF that
develops with the associated lift from this system. The
thermodynamic analysis show that the temperatures will be more
marginal at the surface while colder air moves in aloft with the
base of the trough, helping to erode the pre-existing warm nose. A
wintry mix prevails into the morning on Thursday but may transition
to nearly all snow later during the day with the last of the
precipitation before the conditions dry out with the base of the
trough moving eastward. Snowfall accumulations will continue to be
refined regarding this system but areas mainly to the west across
the Southern Edwards Plateau into the Rio Grande Plains are expected
to see around an inch of accumulation while areas further east see
little to no accumulation. Temperatures have been lowered slightly
with areas seeing highs in the low to mid 30s to the north and east
while locations further west and south may get into the low 40s
during Thursday afternoon. With skies clearing into Thursday night,
do expect another very cold night with temperatures in the teens to
lower 20s when waking up Friday morning.
Upper level pattern transitions to a more zonal flow from Friday
into the weekend with a warming trend back towards climatological
average by Sunday as surface winds finally become southerly as we go
through the weekend. Plenty of sun will be expected early in the
weekend before becoming more cloudy into Sunday. A shortwave trough
passing across the central Plains on Sunday into early Monday sends
a cold front across South-Central Texas sometime Sunday afternoon
into Sunday night. This frontal passage looks to stay generally dry
but a stray light shower cannot be completely ruled out. Drier and
slightly cooler air does push in behind the front into Sunday night
and early Monday morning. Monday then warms up during the day as
solar radiation takes over under mostly sunny skies. Temperatures
continue to warm into Tuesday and midweek with zonal flow aloft and
the return of a southerly surface flow.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 20 35 25 35 19 / 80 20 20 20 0
Austin Bergstrom Intl Airport 19 35 24 35 18 / 80 20 20 20 0
New Braunfels Muni Airport 23 39 28 38 20 / 60 20 30 20 0
Burnet Muni Airport 19 34 22 34 18 / 80 10 20 20 0
Del Rio Intl Airport 26 54 31 41 23 / 20 - 50 40 0
Georgetown Muni Airport 17 34 23 34 16 / 90 20 20 20 0
Hondo Muni Airport 22 48 27 39 19 / 30 - 40 30 0
San Marcos Muni Airport 19 37 24 36 18 / 70 20 30 20 0
La Grange - Fayette Regional 25 36 28 36 20 / 80 50 20 10 0
San Antonio Intl Airport 23 43 28 38 21 / 40 10 30 20 0
Stinson Muni Airport 24 44 28 39 20 / 40 10 30 20 0
Winter Storm Warning until 6 AM CST Thursday for Atascosa-Bandera-
Winter Weather Advisory until 6 AM CST Thursday for Dimmit-Frio-
Area Forecast Discussion...Updated
National Weather Service Peachtree City GA
945 PM EST Tue Feb 16 2021
Have adjusted min temperatures down a couple of degrees
based on trends. Otherwise no changes.
.SHORT TERM /Tonight through Wednesday Night/...
Arctic airmass has finally surged into the CWA this morning
before stalling, bringing with it some light snow showers and even
a dusting of snow in some locations scattered about the state
where a brief heavier snow shower was able to form. Cloud cover
that remained in place across the NWern 3/4ths of the CWA has
finally begun to dissipate in spots allowing the sun to peak
through in some locations. Temperatures this afternoon will warm
only a little in some locations as a result before dipping a
little bit lower tonight.
Aloft, deep 500 mb trough is still in place to the west, so we
remain under a SW flow regime. Another shortwave will move across
the deep south around that trough tonight into Wednesday and
interact with the stalled frontal boundary across the southeast,
generating another surface low that will bring rain and the
potential for some wintry weather to our CWA. Forecast on
Wednesday night is simply put, complex, so please give your local
friendly meteorologist a break if you can. Surface low will send
moisture surging back northward on Wednesday into Wednesday night
with a warm front setting up somewhere in central Georgia. To the
north of this front, isentropic lift will allow for moderate
rainfall to overspread the region, bringing the potential for some
isolated flooding/flash flooding risks, especially where heavier
pockets of rain do form. Some thunder could be possible with this
as well as there is some elevated instability present north of the
front, though not much. To the south, thunder will certainly be
possible as a little more instability is noted, though better
chances for severe weather appear to be on Thursday after sunrise,
and will be covered by the long term discussion below.
The complicating factor to this forecast will be a bit of a wedge
that will be in place across the northern portion of the forecast
area. While not a traditional wedge as we think of it with
forcing from the NE CONUS, this appears to be more remnants of the
very cold air across the area being trapped up against the
mountains given the very southern location of the sfc low. With
cold air in place, some locations in the NE mountains and in NW GA
look to hover at or just below freezing for a few hours while
precipitation overspreads the area. Given very prominent warm nose
at 850 mb reaching 2+ C per HRRR and other soundings, the likely
precipitation type would be either sleet or freezing rain
depending on the depth of the cold air entrenched below. Leaning
towards a more freezing rain solution with what most model
sounding profiles look like in the low levels, and have introduced
that in this package with ice accumulations of a few hundreds of
an inch in parts of NE and NW GA. At the moment, not expecting
much in the way of impacts from this, given it will be 1) short
duration (only a few hours overnight), 2) light accumulations, 3)
marginal temperatures which would likely only allow for glazing of
more elevated surfaces, and 4) would quickly melt as the sun
rises and additional rain moves into the area.
.LONG TERM /Thursday through Tuesday/...
Active weather will be the story across north and central Georgia
on Thursday as an upper-level trough traverses Texas and the Deep
South, while moisture continues to overspread the CWA. A surface
low is progged to develop over the northern Gulf of Mexico and
track northeastward from southeast Alabama into central Georgia
through the day. As such, the threat for strong to severe storms
on Thursday is maximized over central Georgia, where moisture
return along a northward-advancing warm front overlaps with deep-
layer shear and favorable upper-level and lower-level jet
dynamics. As it stands now, SPC has a Slight Risk on Thursday for
the portion of the CWA just south of Columbus and Macon, and west
of Vidalia. However, lower-end instability could prove to be a
limiting factor for storm strength and/or coverage.
In addition to the storm threat, PWATs are progged to reach 1.5"
to 1.75" across much of central Georgia on Thursday (for
reference, the daily max PWAT for February 18th per FFC sounding
climatology is 1.34"). Storm total QPF for this system is 1.5" to
2.0" area-wide with isolated totals up to 2.5". Will need to
monitor for potential hydrology issues, especially across the
southeastern portion of the CWA where some rivers, creeks, and
streams are swollen from recent rains.
As the last of the rain pushes through the eastern CWA early on
Friday morning, cold air will push into north Georgia and meet up
with lingering moisture. A rain/snow mix will be possible across
portions of north Georgia between 04z and 12z Friday, though impacts
appear to be minimal at this time with any accumulations just a
tenth of an inch at most.
Much of Friday, Saturday, and Sunday will bring quiet weather as
surface high pressure spreads across the Southeast beneath upper-
level ridging. The next system to bring precipitation will arrive
on Monday morning. There is much uncertainty this far out, but it
appears that a wintry mix could be possible across the higher
terrain of northeast Georgia in the morning. Elsewhere, liquid
precipitation is expected.
VFR through the period...until the last few hours when ceilings
lower to MVFR around 05z Thursday. Northwest winds less than 8 kts
overnight will shift to the east around 12z with winds in the
10 to 12 kt range.
//ATL Confidence...00Z Update...
High on all elements.
.PRELIMINARY POINT TEMPS/POPS...
Athens 27 50 38 48 / 0 20 100 100
Atlanta 26 49 40 51 / 0 30 100 90
Blairsville 21 45 34 46 / 0 20 100 90
Cartersville 22 49 37 50 / 0 30 100 90
Columbus 28 53 45 63 / 0 30 90 90
Gainesville 27 47 36 47 / 0 20 100 100
Macon 27 54 44 63 / 0 20 80 90
Rome 22 50 37 50 / 0 30 100 90
Peachtree City 25 51 40 54 / 0 30 90 90
Vidalia 32 54 48 72 / 0 20 60 80
Area Forecast Discussion
National Weather Service Fort Worth TX
648 PM CST Tue Feb 16 2021
...New Short Term, Aviation...
.SHORT TERM... /NEW/
/Tonight through Wednesday Night/
Another wintry event is unfolding across the Southern Plains this
evening as snow has spread back into North Texas, mainly north of
I-20. A strong upper trough is spreading into West Texas at this
hour and will continue to deepen overnight thanks to upstream
ridge amplification off the West Coast. Strong synoptic scale
forcing for ascent will overspread the region through tonight, but
the more impressive forcing will come in the form of 925-700 mb
warm advection. It`s rather unusual for us to see snow with
southerly flow below 700 mb as this almost always results in a
strong warm nose and freezing rain events. However, given that
this layer is quite cold from our arctic airmass, it`ll likely
remain below freezing through the event. RAP forecasts of 925-850
mb warm advection peak tonight from midnight to 4 am with rates of
25-35 C/12hr which are pretty incredible rates of warming, yet the
same guidance keeps the thermal profile near or just a touch above
freezing across the Metroplex. This should result in mostly snow
for the Metroplex and areas to the north. Areas to the south will
likely see sufficient warming for areas of sleet and some
freezing rain to occur. The freezing rain is most likely for areas
south of a Lampasas to Hillsboro to Canton line where additional
ice accumulation could approach 1/4 inch. We`ll continue to
monitor this warm advection through the evening though as
additional warming could result in more significant icing across
our southeast counties. Total snow accumulations should range from
2 to 5 inches from the Metroplex northeast...although there could
be some isolated pockets of 6+" near the Red River through
Wednesday morning. Snow amounts will taper off to generally around
an inch or less south of the Metroplex.
All of this activity will move off to the east early Wednesday
morning, however the main trough axis will slowly spread through
the Southern Plains and additional light snow will be possible
through the day mainly along and north of I-20. Little additional
accumulation is expected during this time.
It`ll continue to be cold tonight, although not nearly as cold as
last night, with temperatures in the mid teens areawide. Lingering
cloud cover will hold highs in the mid/upper 20s on Wednesday.
.LONG TERM... /Issued 252 PM CST Tue Feb 16 2021/
After a really rough stretch of winter weather (to put it mildly),
things are looking a lot better through the weekend and especially
into next week. Temperatures should rise above freezing by around
noon on Saturday. After that, we should stay mostly above freezing
through at least the middle of next week as upper-level ridging
builds across the region. The weather looks mainly dry as well.
The one small exception will be on Sunday. On Sunday, a weak
upper-level shortwave trough will move through the Southern
Plains, driving a weak cold front through at the surface. This may
spark a few rain showers in our eastern counties where moisture is
the most abundant, but we are not anticipating any frozen
precipitation or severe weather. Just some light rain, if that.
This weak cold front may also knock a few spots just below
freezing on Sunday night, with a light freeze forecast for areas
north and west of the Dallas/Fort Worth Metropolitan Area.
Heading into next week, the upper-level ridge will build over us,
bringing temperatures into the 60s for the early part of the week,
with overnight lows remaining above freezing. These warmer
temperatures along with abundant sunshine should allow for snow
and ice to melt quickly. Stay tough, Texas. Things are looking
much better by early next week.
VFR prevails throughout the D10 airspace this evening although
conditions will quickly deteriorate as it is snowing above us at
this time. Some dry air aloft will quickly saturate and allow snow
to make it to the ground over the next 1-2 hours. Further snow
development is expected later tonight with IFR expected around
midnight. We`ll have a TEMPO for 1/2SM SN at DFW/AFW from 6-9Z
based on their proximity to the heavier snow bands which should
lie between the Metroplex and the Red River. Otherwise, we`ll
continue to monitor the other sites for further reductions in
visibilities overnight. The main snow should taper off by early
Wednesday morning, but additional light snow may persist into
midday. IFR cigs should prevail most of the day before seeing some
improvement after Sunset Wednesday.
At Waco, some snow will be possible, but warmer conditions aloft
should result in some sleet and freezing rain during the overnight
hours. FZRA should prevail by 8Z and will continue into early
Wednesday morning. IFR will prevail after the precipitation ends.
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 17 27 18 29 13 / 100 60 5 5 0
Waco 18 29 21 31 14 / 100 20 10 10 0
Paris 16 26 18 30 10 / 100 100 10 10 0
Denton 15 26 16 30 9 / 100 60 0 5 0
McKinney 16 26 18 30 10 / 100 70 5 5 0
Dallas 19 27 21 32 15 / 100 50 5 5 0
Terrell 17 27 19 30 12 / 100 80 5 10 0
Corsicana 20 28 22 31 16 / 100 70 10 10 0
Temple 16 31 21 32 14 / 100 20 20 20 0
Mineral Wells 16 26 16 29 11 / 60 20 5 5 0
Winter Storm Warning until 6 AM CST Thursday for TXZ091>095-
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
1004 PM CST Tue Feb 16 2021
955 PM CST
Tweaks to the forecast have been continuing to maintain higher
lake effect snow chances into Porter County, IN through early
overnight, as well as extending clouds over some parts of
northeast Illinois longer and bumping up forecast lows there.
While lake effect snow (for this event) is nearing the end, it has
for most of the evening had a concentrated area of moderate snow
showers into Porter County. This has been well established on low-
level convergence and a presumed meso-low over the southern part
of the lake per analyzed wind streamlines on high-res guidance. As
has been the case, the lake effect parameters are not through the
roof (for instance equilibrium levels of only 6,000 ft), but
because of the very cold low-levels, the dendritic growth zone is
overlapped by the steep lapse rates and cloud depths. We suspect
some parts of Porter County have received around to a little over
2 inches this evening based on radar and webcam imagery, and could
finish with some nighttime totals of 3-4 in isolated spots of
northern Porter. Even if that were to happen, feel the nature of
this after the prolonged event is best handled with G-NOWs, a
Special Weather Statement, and other messaging.
Elsewhere, clouds from the lake effect fetch have meandered across
the south Chicago metro. Think these will stay due to diminishing
850-925 mb flow yet an inversion still in place above that (as
seen on 0230Z aircraft sounding data into MDW). The RAP seems to
be initializing this well and this solution keeps these clouds in
this area for several more hours before then moving them north as
the cloud-bearing blow becomes southerly.
Clouds are having a large influence on temperatures, not surprisingly
with a 1025 mb high moving overhead and fresh snow cover. Those
areas that are clear or can clear for several hours will be subzero,
and already have some of those readings including -6 in Rochelle.
Patchy shallow fog is certainly possible in parts of north
central ILlinois and in the far southern forecast area, though
confidence on that is low. Do not see that being a huge deal if it
develops, but isolated pockets of dense at just a few feet off the
ground is possible.
229 PM CST
The lake effect machine continues this afternoon, but the better
convergence signal has shifted out over the lake and into
northwest Indiana. There is still a loosely organized band with
occasional 25 dBz echoes, but the band is also fairly coherent
across much of the entire length of the lake. Therefore, these
have infrequently reduced visibility in LaPorte county to 1/2SM.
Forecast convergence/low level omega does show an uptick into
Porter county through about mid evening or so, and thus we are not
fully in the clear yet where some impactful lake effect snow may
occur, so use caution if traveling near the lake in northwest
Indiana through the evening.
For the rest of the area, expect cloud cover to slowly erode (where
it currently is now) through the evening as high pressure across the
plains/upper Midwest scoots on in. Light winds could lead to some
fog across north central IL and there is some guidance suggesting
this, but this is of low confidence and will need the evening shift
to take a bit closer look at this. With the light winds and fresh
snowpack, it will be a cold night with subzero temperatures. Some of
the colder guidance pushes -10 across our colder outlying areas of
north central IL.
The snow train continues later Wednesday, though maybe this part of
the ride will be a little less bumpy. Our next disturbance is back
across the Texas panhandle. This will spread toward the region later
Wednesday. This system track will place us on the less favorable
side of the upper jet, though a modest uptick in isentropic ascent
south of Chicago will lead to a generally lighter snow shield during
the afternoon. More limited ascent and drier air near Chicago
suggests the more widespread, though still lighter precipitation may
occur later Wednesday night into Thursday as some interaction with a
northern stream trough aids in better forcing for snow.
300 PM CST
Wednesday night through Tuesday...
As we head into the extended period the high amplitude trough
across the central CONUS will gradually begin to lift to the
northeast late in the week with a quick moving trough following
up behind for the weekend with a warming trend possible early next
Although not as impactful as the previous 48 hours, light snow
remains in the forecast Wednesday evening into Thursday as a
weaker disturbance moves through the trough the area. There
remains considerable variability in the model guidance, similar
to how the past several low QPF snow events we dealt with the
past few weeks were often underdone. Because of this, felt
confident enough to maintain at least "chance" PoPs Wednesday
evening into the overnight hours with a follow up southern-stream
wave moving through. Some lake effect precip may still linger into
Thursday although some of the guidance has backed off on the more
bullish lake effect bands.
Heading into Friday, surface high pressure will set up shop over
the area which should help clear skies out a bit. This combined
with lighter winds and the deep snow pack will allow temperatures
to drop back into the negatives late Friday night into Saturday
morning. Although not as cold as last weekend, wind chill values
in the -5 to -15 range will be possible.
As the upper trough begins to lift east northeast the surface
high shifts into the eastern CONUS which will bring a return of
southerly flow to the area late Saturday into Sunday beginning a
potential warming trend into early next week. A more potent wave
moves through on Sunday with a surface low developing on the left
exit region of a strong upper jet. Model guidance remains somewhat
varied on the precip type for this event. However, with such a
deep snow pack still in place, suspect that the GFS guidance is
still too warm and prefer the ECMWF solution favoring mainly a
snow event for our area. For now keep the rain/snow mix line
mainly along and south of the Kankakee River valley.
For the 00Z TAFs...
533 PM...Forecast concerns include...
Chance for light snow Wednesday afternoon into Wednesday evening.
Chance for light fog early Wednesday morning.
Lake effect snow showers continue into northwest IN, mainly east
of gyy though there have been a few flurries here at lot late
this afternoon along with some virga and carried flurries at gyy
for a few hours this evening. Otherwise, dry weather is expected
until Wednesday afternoon when there will be another chance for
light snow across the entire area. There remains some uncertainty
with this system as it will likely be weakening as it lifts across
the area. There are also some timing differences and opted to
carry tempo mention centered around 00z but some prevailing light
snow mention may be needed as trends emerge. If light snow
develops...vis in the 2sm range can be expected along with mvfr
High pressure will move across the area with light westerly winds
likely becoming light and variable or calm tonight. Winds will
turn southerly Wednesday morning and southeasterly by afternoon.
The light winds and clearing skies may lead to some light/shallow
fog developing away from the Chicago metro area. Confidence if
very low and did not include any fog mention but its possible for
some fog to develop by morning, especially in the usual/rural
A bkn/ovc 4-5kft deck over the Chicago area is expected to slowly
shift southeast and dissipate this evening into the overnight
hours but low confidence for timing. A mid deck will spread across
the area Wednesday ahead of a lower, 3-4kft, vfr deck in the
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Area Forecast Discussion
National Weather Service Miami FL
903 PM EST Tue Feb 16 2021
The cold front that gradually moved across South Florida during
the day today has stalled across the nearshore Atlantic waters off
South Florida -- evident via northerly surface winds across the
east coast metros and a stalling band of pre-frontal convection
over the Atlantic waters. As the primary mid-level shortwave
trough ejects offshore the New England states, there may be a
tendency for rich moisture (PWs near 2 inches) to lift back
northward across the eastern portions of South Florida along the
stalled boundary overnight.
While large-scale forcing for ascent will be minimal, northward
positive theta-e advection and potentially coastal/frictional
convergence could allow for mesoscale ascent and re-development of
coastal convection during the overnight hours. In addition,
latest RAP analysis suggests that a mesoscale low may be
developing offshore Palm Beach County which could further aid in
northward moisture transport and associated continued instability.
Generally west-southwesterly steering currents aloft could
potentially aid in convective training and backbuilding along the
immediate east coast metros during the overnight hours, which
would raise increasing flooding concerns owing to todays heavy
rainfall and high tide around midnight. The overnight flooding
risk remains conditional upon convective residence time along the
east coast metros.
The 00Z MFL RAOB shows a favorable environment for heavy rainfall
with a deep warm cloud depth, PW of 1.82 inches, and weak mid-
level lapse rates. In addition, marginal deep-layer shear around
20 to 25 knots could aid in brief updraft organization and
localized heavy rainfall. The areas that got hit hardest with
heavy rainfall today are portions of the coastal/metro Miami area
and portions of metro Broward County. The WPC continues to
maintain a marginal risk of excessive rainfall/flash flooding for
the east coast metros overnight. Please keep up with the latest
from NWS Miami and the WPC.
.PREV DISCUSSION... (Issued 719 PM EST Tue Feb 16 2021)
Brief periods of IFR are still possible over the Atlantic
terminals through around 05Z as a front is stalling around South
Florida. Main impacts will be low cigs, possibly in the bkn004-005
range with isolated heavy rain. Otherwise, VFR is expected through
15Z, then periods of MVFR cigs/vis may again develop Wednesday
afternoon. Winds should remain light and variable through 15Z.
PREV DISCUSSION... (Issued 239 PM EST Tue Feb 16 2021)
Short Term (Tonight through Wednesday):
A cold front will continue to move eastward generally through the
region this afternoon and evening. The problem is where exactly does
this front stall? Over the Gulf Stream would be enough to transition
winds to an offshore flow and reducing rain chances. However, a
stall right over the Atlantic metro could be bad news. A stall over
the metro would mean not only continued rain and storm chances, but
perhaps some flooding potential as well. In fact, PWATS from this
morning`s sounding are right around 1.8" or so...which to put that
into perspective is roughly within the 99 percentile for this time
of year. With the boundary over and a unidirectional wind profile,
hydro concerns may arise, despite antecedent conditions being a bit
on the drier side. Rate could easily overpower absorption...plus the
urbanized regions are always slow to drain.
Severe weather? Still possible through the afternoon and perhaps
early evening hours. CAPE values from this morning`s sounding were
also a bit impressive for 7am. Generally around 2200 J/KG. Although
heating will take place, there will be cloud cover, which will
overall limit destabilization during peak heating. Limited upper
ascent will also keep any severe threat on the lower end of the
scale. That said, with surface lifting (front) and plenty of
instability, continued mentioning strong to isolated severe storms
through the remainder of today.
Going into Wednesday, the front will slowly begin to move northward.
Since we will still be within close proximity, continued rain
chances through peak daytime heating. A few thunderstorms can be
expected, but the lackluster parameters should continue to limit the
overall severe weather threat. We`ll need to continue to watch
exactly where showers and storms develop and if the aforementioned
scenario with the front stalling over the Atlantic comes to
fruition...what impact would that have on the possible hydro
situation. Regardless temperatures should generally remain above
average for both overnight low and daytime highs through the period.
Long term (Wednesday Night through Monday):
Models show a rather short-lived ridging/drier period from Wed night
through Thursday night as high pressure establishes over the region
in the wake of the front`s departure. Subsidence and drier air will
bring POPs down to single digits by Thursday afternoon, along with
afternoon highs hitting the mid to upper 80s.
For Friday, models depict a longwave trough over the Gulf region
approaching and dragging a sfc front with it. So far consensus is
not too excited about potential for significant impactful weather
with this frontal passage, with mainly a narrow line of showers and
embedded thunder moving across SoFlo associated with the leading
edge of the boundary. Current timing has the front clearing the
peninsula Friday afternoon or evening, followed by a short period of
lingering post-frontal clouds and patchy light precipitation.
Drier and much cooler air will then pour into South Florida Friday
night through next weekend. Temperatures will remain well above
normals through Thursday, then highs cool down into the low-mid 70s
for the weekend behind the FROPA.
Quiet weather continues into early next week easterly flow returning
and slowly moderating temperatures.
Showers and thunderstorms are expected over the local waters as a
frontal boundary stalls across the area. Locally hazardous boating
conditions are possible with lightning, gusty winds, and waterspouts
as potential hazards. More favorable marine conditions return by
late week as the front lifts away to our north and high pressure
rebuilds into the area.
Elevated rip current potential will continue along the Palm Beach
County Beaches through Wednesday. Although winds may shift to
offshore, the northeasterly swell will continue to create rip
.PRELIMINARY POINT TEMPS/POPS...
Miami 71 83 74 85 / 30 30 0 0
West Kendall 69 85 72 86 / 30 30 0 0
Opa-Locka 69 83 72 84 / 30 30 0 0
Homestead 69 83 73 84 / 30 20 0 0
Fort Lauderdale 71 83 74 85 / 30 40 0 0
N Ft Lauderdale 71 82 73 83 / 40 40 0 0
Pembroke Pines 70 84 73 85 / 30 40 0 0
West Palm Beach 68 82 71 83 / 40 40 0 0
Boca Raton 70 83 73 85 / 40 40 0 0
Naples 65 83 69 83 / 10 20 0 0
Tonight/Wednesday and Marine...HVN
Wednesday Night through Tuesday/Aviation...AR
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Area Forecast Discussion
National Weather Service Paducah KY
749 PM CST Tue Feb 16 2021
Issued at 749 PM CST Tue Feb 16 2021
Initially clear and nearly calm conditions have allowed
temperatures to plummet over much of the region. Many locations
have already reached zero or below. The RAP guidance seem to have
the best clue to sub-zero temperatures over the snowpack, so
sprinkled it in liberally. As clouds increase and winds pick up a
bit, temperatures are likely to rebound quite a bit by daybreak
UPDATE Issued at 552 PM CST Tue Feb 16 2021
The AVIATION section has been updated for the 00Z TAF issuance.
.SHORT TERM...(Tonight through Thursday night)
Issued at 400 PM CST Tue Feb 16 2021
Big challenges in the short term. Confidence levels medium at
Yet another mid level short wave is expected to shift eastward
into the Plains later tonight and Thursday, as surface low
pressure lifts ene out of the nrn Gulf and into the southeastern
part of the country. A leading northern branch short wave is also
expected to lift ne into the MO River Valley overnight. This wave
will likely bring an are of light snows to portions of se MO
overnight, but the system flattens and runs into dry air as is
tries to make its way across the MS River Wednesday AM. Will leave
the current winter weather advisory in place to cover generally a
1-2" snow possibility (locally higher near the Ar/MO border)
toward the AM commute.
The main short wave coming out of the southern Plains is a bit
problematic. The global EC/GFS deterministic models show less
phasing of another H50 northern branch feature with the stronger
southern branch as it moves farther east Wednesday into Thursday,
thus shunting most of the more significant moisture off to our
south in TN.
However, the 18Z NAM, the 12Z GEFS and the 12Z HREF indicate more
phasing of the branches as the system moves east, and hence
suggest a greater snow potential farther north into our CWA, esp
Wednesday night into Thursday. I decided at this point to lean
more toward this type solution, especially given the tendency for
north/west shift of precip shields with time during past/recent
Therefore, along with collab from adjacent WFOs, have opted to go
ahead and issue a winter storm watch with this forecast package
for about the southern half of the forecast area (east of the MS
River). Many of these aforementioned higher resolution models
suggest the potential for a good 2-4" swath of snow late
Wednesday/Wednesday night into at least Thursday morning, with
locally higher amounts possibly esp near the KY/TN border region.
It is important to note that confidence levels at this time are
at the low end of what we normally like to have for winter storm
watch issuance. Stay tuned, as adjustments will be probable as the
possible event nears in the next 24 hours.
.LONG TERM...(Friday through Tuesday)
Issued at 400 PM CST Tue Feb 16 2021
After a week of winter storms, Friday will finally bring a start to
quieter conditions, but not yet warming. Behind the Wednesday-
Thursday system the trough deepens a little more across the area
bringing yet another frigid day with highs in the 20s. Partial
cloudiness will offset some of the temperature drop overnight, but
lows in the mid single digits to lower 10s are likely due to
relatively light winds and continued snow cover.
On Saturday, the stubborn upper-level trough is finally pushed off
to the east, beginning a northwesterly flow aloft and a warming
trend. High pressure in the east and a developing low emerging from
the Colorado Front Range will help keep winds southerly across the
Quad State. While warm advection will be ongoing, snow cover will
keep temperatures limited mainly to the low to mid-30s for Saturday.
Heading into Saturday the streak of days at or below freezing is
expected to be at 10 days for Paducah (tied for 4th longest) and 11
days for Evansville (tied for 11th longest) assuming these continue
through Friday. Saturday may add one last day to those counts.
If not Saturday then Sunday will bring an end to below average
temperatures, with highs near or above 40 degrees. The low pressure
system in the Central Plains is expected to move northeastward,
crossing to the north of the Quad State overnight. The operational
models are in moderately high agreement on a line of mainly rain
showers (some mixing of snow is possible Sunday night) developing
from the Great Lakes down towards the Gulf Coast. The Canadian
brings the line through during the day while the GFS/ECMWF wait
until Sunday night. Ensembles seem to be somewhat similar on average
to the operational. QPF remains fairly light, between a tenth and a
quarter of an inch, primarily as rain. While the line of rain Sunday
would likely be accompanied by a frontal passage, the disruption to
the warming 2trend and southerly flow is likely to be temporary,
with highs potentially near 50 by Tuesday.
Issued at 552 PM CST Tue Feb 16 2021
MVFR ceilings and some areas of light snow may linger through the
evening in the KHOP area, but elsewhere, VFR conditions are
forecast for most of the night. Our next round of light snow will
overspread southeast Missouri overnight, and may reach KCGI and
KPAH by 12Z. A period of MVFR snow is expected at those sites, but
MVFR ceilings will arrive a few hours later as visibilities
improve. Some VFR light snow may reach the other TAF sites by
18Z, and cannot rule out a very brief period of MVFR snow at KOWB.
MVFR ceilings should prevail over the entire area through the
afternoon. The next and more significant area of snow may reach
KCGI and KPAH near the end of the period.
IL...Winter Storm Watch from Wednesday afternoon through Thursday
afternoon for ILZ088>094.
MO...Winter Storm Watch from Wednesday afternoon through Thursday
afternoon for MOZ112.
Winter Weather Advisory from midnight tonight to noon CST
Wednesday for MOZ076-086-087-100-107>111-114.
KY...Winter Storm Watch from Wednesday afternoon through Thursday
afternoon for KYZ001>013-015>017-020>022.
Area Forecast Discussion
National Weather Service Riverton WY
221 PM MST Tue Feb 16 2021
.SHORT TERM...Tonight through Wednesday night
Light snow continues to fall across the west as this latest system
continues to overperform across the higher peaks. The northwest flow
pattern will continue, and with it, chances of snow across the
western mountains. In terms of additional snowfall amounts, the
higher peaks of the Tetons and Salt/Wyoming Range will see another 6
to 8 inches with locally higher amounts possible. The Absarokas and
Gros Ventres will see another 2 to 4 inches, again with locally
higher amounts, especially along the eastern edge of Yellowstone
Park. The western valleys are not looking at much additional
accumulation with generally 1 to 2 inches expected. These amounts
are through Wednesday morning. Heavier snow will fall through 11 PM
Wednesday morning, a quick-hitting shortwave will sweep northern
Wyoming with a piece of energy that will cause some higher snowfall
rates early Wednesday afternoon. This energy will also bring some
snowfall to northern Wyoming. This snow will be banded in nature,
which means snowfall amounts are generally very difficult to pin
down. Kept general PoPs across the Bighorn Basin and Owl Creeks and
into northern Johnson County tonight through Wednesday afternoon to
account for the uncertainty in the bands. The HRRR and 4km NAM both
show banding coming off of the southern Absarokas and Bighorns,
which could mean some of the bands may reach as far as Riverton and
Lander as well as Casper, but again, uncertainty is very high with
banded snowfall like this. Amounts under the bands doesn`t look to
be more than an inch or two, as there is not much moisture and these
bands will be quick-moving.
Temperatures will continue to push closer to normal. Some locations
are seeing 30 for the first time in over a week today. Those same
locations will come close to 30 again tomorrow, but the quick-
hitting system and cloud cover will keep temperatures cooler than
the otherwise would be for tomorrow. Lows will continue to be in the
low teens to single digits, but should be above zero east of the
Divide. The Green River Basin and cold valleys in Yellowstone may
see lows a few degrees below zero, especially Wednesday night if
skies clear out enough. Winds will remain mostly light through the
next day or so with some breezy conditions during the afternoon
across the southern Wind Corridor, including Rock Springs. Winds
will diminish overnight, as is the norm, and increase again after
.LONG TERM...Thursday through Tuesday
The period should start off fairly quiet with decreasing snow
showers as moisture gradually moves away and transitory ridging
builds across the Cowboy state. This should bring a period of around
24 hours or so of mainly dry and quiet weather.
The next in the series of Pacific waves will move into the west on
later Thursday night into Friday with the next chance of snow. At
this point, this does not look like a huge storm. However, it could
be enough for some advisory level snow, especially in the mountains.
It could also bring some snow to Interstate 80 Friday morning,
causing some travel problems.
The big question in this period is what happens with the Saturday
system. And like the previous shifts, the models are not in good
agreement with the position of the jet streak that will define where
the snow will be. The GFS continues to be further north and brings a
good stripe of snow across much of the southern two thirds of
Wyoming from Saturday into Saturday evening. Meanwhile, the European
is further south and keeps the snow largely across southern Wyoming,
although it has trended a bit further north than the previous run.
For now, we made few changes to continuity but this has the
potential to be a decent snow for many areas if things work out
Uncertainty increases starting on Sunday. A few waves will move
through what looks to be a west to northwest flow. At this point, it
looks to more of an upslope / downslope pattern with some snow
showers in the west and mainly dry conditions east. Details on
timing and intensity are still uncertain though. Source region of
the air mass looks to remain largely Pacific, so any outbreaks of
Arctic air look unlikely.
West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals
Steady snow should taper to showers tonight at KJAC, although
showers remain possible through the night with occasional mountain
obscurations possible through the night. Largely VFR conditions will
occur elsewhere although a stray shower can`t be ruled out at KBPI
and KPNA. Gusty winds at KRKS should decrease tonight with lighter
wind expected tomorrow.
East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals
VFR conditions continue through the next 24 hours for most
locations. A few locations will have the chance of snow showers or
snow bands into the evening, but confidence is low in pinpointing
them. As a result, we have gone with VCSH for most locations. Any
snow showers should end late tonight. More snow showers are possible
tomorrow but should not be as numerous. Occasional mountain
obscurations will be possible in any snow shower or snow band.
Snow continues across western areas through Wednesday. Some snow
banding is possible across northern areas tonight and Wednesday.
Snow bands may reach as far south as the central Wind River Basin.
Western mountains will see another 3 to 6 inches with higher amounts
in the Tetons ans Salt/Wyoming Ranges. Valleys and areas east of the
Divide will see an inch or two of snow through Wednesday. Smoke
dispersal will be poor to fair with light winds expected. Most areas
will remain mostly cloudy through Wednesday and clearing Wednesday
night into Thursday. Temperatures will be more seasonal through the
rest of the week. The next significant chances of snow will be
Friday through the weekend.
Winter Weather Advisory until 11 PM MST this evening for WYZ012-